The magic number for notebook designers in the near future just might be eight--as in the hours of a full workday.

A somewhat outlandish idea a few years ago, the eight-hour notebook is moving closer to reality as promising trends in battery materials and power consumption converge. If all goes well, within three to four years, portable PCs could see battery life double from today's four-hour stretch.

Chipmaker Intel, in fact, is so bullish on the matter that it recently moved up a deadline for notebook makers by two years. It's now asking them to produce by 2008 thin and light notebooks that can run for eight hours without the use of additional external batteries, said Mooly Eden, vice president of the company's mobility group.

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Within three to four years, portable PCs could see battery life double from today's four-hour stretch.

Bottom line:Rejoice, laptop owners. Battery life, a crucial consideration for fans of portables, is getting plenty of attention from makers of chips and PCs.

Notebooks are an area of keen interest for Intel and other processor companies. Chips for those systems generally sell at higher prices than their desktop counterparts, and are more profitable to boot. The notebook segment of the PC market is growing fast, and currently accounts for about 30 percent of the PC processors shipped.

Computer makers, meanwhile, are working on making notebooks lighter to help get the most life out of whatever type of battery they use.

Four hours is the current standard for thin notebooks, although that allotment remains elusive in real life.

"The spec says this, but it depends on some degree on usage," said Roger Kay, an analyst at IDC. "Batteries also don't have that life for long. They might have four hours at the beginning of the year, but if you start doing more multimedia, it might go down to 2.5 hours by the end of the year."

The biggest gains in battery life are likely to come from the guts of the batteries themselves.

For instance, start-up Zinc Matrix Power has devised a way to produce batteries out of zinc alkaline that can provide more energy than conventional lithium ion batteries but don't take up any more space inside a laptop, according to Mike Trainor, chief mobile technology evangelist at Intel.

Competitor Pionics has designed a lithium ion battery that could offer similar performance. Others are working on variations such as lithium polymer.

Can you say 'supercharged'?
"By changing the metals in the cathode you can change the capacity curve of the battery," Trainor said. "The next question is whether you can make a cathode with that mix of metals into mass production."

The equation for studying battery performance, Trainor said, is relatively straightforward: Divide the amount of energy stored in batteries--measured in watt hours--by the average power consumption of a notebook.

Today, a high-performance thin and light notebook (typically one that weighs less than 5 pounds) might come with batteries that can provide 58 watt hours of energy. The average power consumption of those notebooks, however, comes to 12 watts or more. Hence, battery life totals about four hours, at best.